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Session 117 - Galactic ISM.
Oral session, Thursday, January 16
Harbour B,
The unexpected broad 1809 keV line from decay of radioactive ^26Al observed by the Gamma Ray Imaging Spectrometer (GRIS) balloon experiment provides a powerful new tool in probing the ISM structures in the Galaxy. To explain the observed line width and intensity, simple but robust astrophysical calculations strongly favor the existence of both large volume filling factor and large sizes of a low density, hot medium in the Galaxy in general and on spiral arms and in the Galactic center region in particular. Future \gamma-ray observations by INTEGRAL will provide a definitive answer to these outstanding questions.
